Welcome back! Let us explore the many varieties of QUARTZ! How are there so many different varieties? It’s all in the chemistry!

Varieties of quartz. Source from GeologyIn.com

Agate – Multi-colored, banded chalcedony. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.

Onyx Agate where the bands are straight, parallel and consistent in size.

Jasper Opaque cryptocrystalline quartz, typically red to brow. The common red color is due to iron(III) inclusions.

Tiger’s Eye Fibrous gold to red-brown colored quartz, exhibiting the sheen depending on what angle you hold it to the light.

Aventurine Translucent chalcedony with small inclusions (usually mica) that shimmer. The most common colour of aventurine is green, but it may also be orange, brown, yellow, blue, or gray.

Amethyst Purple, transparent. Amethyst is a semiprecious stone and is the traditional birthstone for February.

Rutilated quartz Contains acicular (needle-like) inclusions of rutile.

Carnelian Reddish orange chalcedony, translucent. The color can vary greatly, ranging from pale orange to an intense almost-black coloration.

Carnelian sample from mindat.org

Citrine is a variety of quartz whose color ranges from a pale yellow to brown due to iron impurities. Natural citrines are rare.

Prasiolite Mint green, transparent. It is a rare stone in nature.

Rose quartz Pink, translucent. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the massive material.

Milky quartz White, translucent to opaque. The white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation, making it of little value for optical and quality gemstone applications.

Smoky quartz is a gray, translucent version of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque.

Chalcedony The term is generally only used for white or lightly colored material. Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown.

Mtorolite also known as chrome chalcedony, it is principally found in Zimbabwe.

Chrysoprase is a green variety of chalcedony, which has been colored by nickel oxide. Its color is normally apple-green, but varies to deep green.

Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood, giving heliotrope its alternative name of bloodstone.

A sample of Bloodstone (Heliotrope). Source: GeologyIn.com

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